This invention relates to an electrically operable ceramic valve of a beverage machine which is adapted for preparing beverages suitable for consumption, comprising at least one inlet, at least one outlet, and at least one liquid flow channel: extending between the inlet and the outlet, the ceramic valve further comprising a first ceramic subhousing and a second ceramic subhousing through which the liquid flow channel extends and which are adapted to be displaceable along each other by means of an electric drive, for controlling a liquid flow from the inlet to the outlet, the liquid flow channel comprising a bend extending at least for a part in the second subhousing, while the liquid flow channel in an opened condition of the valve extends upstream of the second subhousing and downstream of the second subhousing in at least the first subhousing, and the first subhousing comprises a first aiding surface having at least one outflow opening and at least one inflow opening, the liquid flow channel extending from the first subhousing through the outflow opening to the bend in the second subhousing, and the liquid flow channel extending from the bend through the inflow opening in the first subhousing, while the second subhousing comprises a second sliding surface.
Such a ceramic valve is known from EP-A-0 361 183. In this valve, in preparing beverage s for consumption, beer is fed from a vat to a first inlet. The second subhousing is then in a second extreme position. For cleaning the valve, the second subhousing is slid relative to the first subhousing into a first extreme position. Thereafter, to a second inlet, a cleaning agent is supplied, which flows back via the second subhousing to the first subhousing to subsequently leave the first subhousing via the first inlet which functions as outlet for cleaning. A disadvantage of the known valve is that sliding the second subhousing relative to the first subhousing is accompanied by a relatively great friction between the subhousings. Accordingly, this requires much energy. The valve according to the invention is intended to provide a solution to this disadvantage and is characterized in that the first sliding surface is provided with at least one circumferential edge closed in itself which projects relative to a part of the first sliding surface where this edge is not situated, in the direction of the second sliding surface, so that an upper side of this projecting edge abuts against the second sliding surface and forms a sealing with the second sliding surface, or that the second sliding surface is provided with at least one circumferential edge closed in itself which projects relative to a part of the second sliding surface where this edge is not situated, in the direction of the first sliding surface, so that an upper side of this projecting edge abuts against the first sliding surface sand forms a sealing with the first sliding surface.
The upright edge has the advantage that in use little resistance is sustained when the second subhousing is displaced relative to the first subhousing, since in that case the contact surface of the first and the second subhousing is defined by the upright edge.
A further disadvantage of the known valve is that the first inlet is not suitable for functioning as outlet when liquids are delivered for preparing beverage suitable for consumption. When the second subhousing is in the first extreme position, so that the second inlet is blocked, the first inlet which would have to function as outlet is in open communication with a third outlet, which is undesirable from a hygienic and practical viewpoint. According to another aspect of the invention, that problem is also solved. The invention according to this aspect concerns an electrically operable ceramic valve of a beverage machine which is adapted for preparing beverages suitable for consumption, comprising at least one inlet, at least one outlet, and at least one liquid flow channel extending between the inlet and the outlet, the ceramic valve further comprising a first ceramic subhousing and a second ceramic subhousing through which the liquid flow channel extends and which are adapted to be displaceable along each other by means of an electric drive, for controlling a liquid flow from the inlet to the outlet, the liquid flow channel comprising a bend extending at least for a part in the second subhousing, while the liquid flow channel in an opened condition of the valve extends upstream of the second subhousing and downstream of the second subhousing in at least the first subhousing, and the first subhousing comprises a first sliding surface having at least one outflow opening and at least one inflow opening, the liquid flow channel extending from the first subhousing through the outflow opening to the bend in the second subhousing, and the liquid flow channel extending from the bend through the inflow opening into the first subhousing, while the second subhousing comprises a second sliding surface, and the second subhousing is slidable along the first subhousing between a first and second extreme position, and in the first extreme position the inflow opening of the first subhousing and the outflow opening of the first subhousing form a fluid communication with the opening in the second subhousing, characterized in that in the second extreme position the inflow opening of the first subhousing and/or the outflow opening of the first subhousing is closed off by the sliding surface of the second subhousing.
A ceramic valve of the type described in the opening paragraph is further known from EP-0 307 497. In this known valve, the first subhousing and the second subhousing consist of rotatable ceramic disks located against each other and equipped with distribution channels. A disadvantage of the known apparatus is that additionally, a third subhousing is present, while each of the subhousings are of disk-shaped design and the second subhousing is clamped between the first subhousing and the third subhousing. The second subhousing is adapted to be rotatable relative to the first and third subhousing. Because the second subhousing is clampingly received between the first and Bird subhousing, the rotation of the second subhousing will take relatively much energy Moreover, the accuracy with which the second subhousing could be set relative to the first subhousing is relatively low.
The ceramic valve according to the invention is characterized in that the liquid flow channel comprises a bend extending at least for a part in the second subhousing, while the liquid flow channel in an opened condition of the valve extends upstream of the second subhousing and downstream of the second subhousing in at least the first subhousing;
Since the bend extends in the second subhousing, the valve only needs to comprise two subhousings adapted for relative displacement.
In particular, the second subhousing is displaced (translated) along the first subhousing by means of the electrical drive for controlling the liquid flow. The translation of the first subhousing relative to the second subhousing has the advantage that it can be made of very simple design.
Preferably, in the sliding surface of the second subhousing an opening is present through which the liquid Sow channel extends from the outflow opening of the first subhousing and through which the liquid flow channel extends from the second subhousing to the inflow opening of the first subhousing. Then the bend can in fact consist of not more than a cavity in the sliding surface, while the cavity also contains the opening mentioned.
For a highly advanced embodiment of the valve, it holds that the liquid flow channel has a cross section of an oval shape at at least one position in the interface between the first subhousing and the second subhousing. What is achieved if, in addition, a long axis of the oval shape is at least substantially directed perpendicularly to a direction of movement of the second subhousing relative to the first subhousing, is that in the direction of movement only a relatively small displacement of the second housing relative to the first housing is needed to bring the valve from an opened condition to a closed condition and vice versa. Moreover, a displacement of the second housing relative to the first housing when the valve is nearly closed corresponds with a change in the passage area of the valve which is relatively small relative to the change in the passage area occuring upon the same displacement of the second housing relative to the first housing when the valve is almost completely opened A fine adjustment of a relatively small passage area is thus enabled.